1. Field of the Invention
This invention relates generally to concrete products forming machines (CPMs) and more particularly to compression shoes used in such machines that form molded products.
2. Description of the Prior Art
Prior art machines for forming concrete products within a mold box include a product forming section comprising a stationary frame, an upper compression beam and a lower stripper beam. The mold assembly includes a head assembly that is mounted on the compression beam, and a mold box that is mounted on the frame and receives concrete material from a feed drawer. An example of such a system is shown in U.S. Pat. No. 5,807,591 which describes an improved concrete products forming machine (CPM) assigned in common to the assignee of the present application and herein incorporated by reference for all purposes.
Current production process consists of a mold containing forming cavities in which concrete material is filled. During each machine cycle, a pallet is brought in contact with the bottom surface of the mold, closing the bottom side of the cavities. Concrete material is deposited into the top of each cavity and then vibrated to concentrate the material. During this cycle a compression shoe is inserted into the top surface of the cavities which then compresses further and forms the top of the concrete material to a specific surface configuration.
Conventional compression shoes are comprised of case hardened steel that is machined precisely to fit the cavity opening and to create a specific shape characteristic into the top formed surface of the concrete material. The compression shoe when contacting the top surface of the concrete material causes concrete material to adhere to the contact surface. This adherence can build up during the multiple cycle process causing the original surface to be altered and the concrete product being formed to have inferior appearance.
A known method for addressing the build-up of concrete on the compression shoe during multiple cycles is to apply heat to the compression shoe to elevate the temperature adequately to hydrate the surface tension between the compression shoe and the concrete material during the forming process. This method, however, is highly energy inefficient since heating energy must be constant applied to the compression shoes, thus elevating the temperature of the work environment as well as possibly degrading the lifetime of the shoe.
Accordingly, there is need for alternate methods for preventing the build-up of material on the compression shoes and enhancing their wear characteristics.